1. Field of the Invention
This invention relates to an inspection device for inspecting defective images and adhering foreign matters of an inspection object on which images are formed, such as a wafer, a liquid crystal panel, a mask, and so forth, and an inspection method for this inspection device.
2. Description of the Related Art
In a semiconductor production process, for example, foreign matters existing on a semiconductor substrate or pattern defects created during the production process cause defects such as inferior insulation and short-circuit and lower a production yield. Smaller foreign matters or defects, if any, may result in a critical problem with further miniaturization of semiconductor devices and more delicate defect detection becomes therefore necessary.
The defects and the foreign matters are detected in an early stage of a production process by using a semiconductor inspection device on a semiconductor production line, for example, and the causes of the defects are specified and are fed back to the production process so as to improve the production yield.
However, an equivalent inspection sensitivity cannot always be obtained by an inspection device of the same type and even when the same inspection object is inspected, differences often occur in the number and kind of defects detected.
To reduce the inspection sensitivity difference (machine difference) among the inspection devices (machines), it is import to conduct adjustment of the inspection sensitivity and to keep conformity but it is practically difficult to render the inspection sensitivity of the inspection devices (machines) uniform owing to variance of performances of elements that constitute the inspection device (machine). Therefore, a correction method for reducing the variance has been required.
JP-A-2005-201782 as one of the prior art technologies of this kind discloses a technology for reducing noise resulting from a detection system by combining a plurality of sensors and correcting signals.
JP-A-2003-346698 describes a method for correcting influences of fluctuation resulting from non-uniformity of electron beam dosage and time by using a plurality of detectors in an electron beam apparatus and individually executing gain correction and offset correction for each of the detectors.
The reference described above, i.e. JP-A-2003-346698, describes also a method for correcting non-uniformity of signal intensity inside a visual field by dividing a two-dimensional sensor into a plurality of regions and correcting a digital level of an output signal for each of the regions divided.
Another reference JP-A-4-362790 discloses a method for correcting light power fluctuation by an exposure time in a scan type sensor.
Still another reference JP-A-2006-250739 describes illumination light correction in an illumination optical system by changing a shape of a reflecting surface to execute aberration correction.